HR 8734 Piscium

THE PLANET

The circle at upper left shows the location of the class G "subgiant"
(but probably dwarf) HR 8734 Piscium relative to stars of Aquarius.
The star is near the border between the two constellations, though
just over to the Pisces side. HR 8734's planet has a mass at least
1.28 times that of Jupiter. It orbits its star with a period of
only 7.11 days at an average distance of but 0.07 Astronomical
Units (10.5 million kilometers, 6.5 million miles, 18 percent
Mercury's distance from the Sun, 13 stellar radii), the closeness
making it one of the many "hot Jupiters." An orbital eccentricity
of about 12 percent takes the planet between 0.08 and 0.06 AU from
its star.

THE STAR

HR 8734 Piscium is a mid-sixth magnitude (6.18) class G8 star in Pisces that lies just over the
constellation's border with Aquarius. Too
faint to have a proper or Greek letter name, it is known best
by its numbers in the Bright Star(HR) and the Henry
Draper (HD) Catalogues.
From a distance of 64 light years, it shines with a luminosity of
1.16 times that of the Sun from a surface at
5649 Kelvin (130 degrees cooler than the Sun), which tells of a
star with a radius 1.13 solar and a mass very close to that of the
Sun. Though classed as a subgiant, the star is really on ordinary,
though ageing, dwarf. To have a higher luminosity and lower
temperature, the star must be older and more evolved than the Sun
by perhaps a couple billion years. Like most stars with planets,
54 Psc is rich in metals, its iron abundance (relative to hydrogen)
quite high, 2.3 times solar. From the planet the star would appear
some 15 times larger in angle than the Sun does from Earth.